1. Field of the Invention
The present invention relates generally to golf clubs, and more particularly to multi-track adjustable golf clubs.
2. Background of Related Art
Golfers have many different swing types. This variety in swing types means that different golfers contact the ball in different ways. Each different swing can impart a different spin and/or flight trajectory to the ball. The ball may “draw” or “fade,” for example, based on the type of swing the golfer uses. Similarly, the ball may have a trajectory that varies with the spin rate of the ball following contact. A ball with a higher spin rate may rise more after contact than a ball with a lower spin rate would rise. These different trajectories can be desirable when intended and undesirable when unintended.
Golfers' strokes also can change over time. A golfer who previously contacted the ball such that the ball would rise and draw, for example, may modify his swing or stance so that he contacts the ball such that the ball rises less and fades. If the golfer's club is set up to correct a particular swing, and that swing changes, the club may no longer be suitable for the golfer. Adding the ability to adjust a club allows the club to change with the golfer's swing and provide the desired contact and trajectories.
In addition to a golfer's swing, the physical specifications, or inherent characteristics of the club head may also influence trajectory. In general, for a metal wood head, as the center of gravity (“COG”) is located further from the shaft axis the club is more fade biased. Conversely, as the COG is located closer to the shaft axis the head is more draw biased. Similarly, a COG located nearer the face may tend to reduce spin and lower the effects of lift force on the ball thus promoting a lower ball flight. The opposite is true for a COG that more rearward (further from the face).
A golfer may desire more distance on the trajectory of his shots. Since the rules of golf limit the spring like effect from the face, an alternate way of generating more distance is to optimize the ball launch for spin and launch angle. This condition allows the ball to fly further and straighter due to improved aerodynamic performance. Having an improved COG location optimized for each individual golfer can improve the launch conditions of the ball, thus having an adjustable weight/COG metal wood can provide additional distance if the player can easily and intuitively find their appropriate weight setting. Traditional golf clubs have predetermined weighting, which results in a fixed COG location. Thus, the clubs cannot be easily modified to compensate for issues with a golfer's swing, such as, for example, unintended draw or fade.
Some prior attempts to address this problem have involved adjustable weight drivers that make use of weight screws. One of the weakness of such systems is that weight screws are not efficient for weight movement, since swapping positions of a first screw with mass A with another screw with mass B results in a net mass movement of A-B. This inefficiency often requires significant weight to be added and subtracted from a club, which may have undesirable effects on other characteristics of the club's performance.
Other attempts to address this problem include single-track systems. In these systems, the track may follow the skirt of the driver in an attempt to be more efficient than using weight screws for weight displacement, but they still lack the ability to isolate the weight movement in the front/back and toe/heel direction, leading to less intuitive self optimization. Some single-track systems that are parallel to the face and in close proximity to the face have little or no ability to adjust COG depth and are likely very front weighted due to the mass of the track, thus no ability to increase spin and trajectory height by COG adjustment in the front/back direction. Current single-track systems also tend to have closed-ended tracks. Tracks with closed ends, however, do not allow for easy movement of the weights from one track to another if the golfer needs more weight in a given area of the head. Additionally, close ended tracks are more difficult and expensive to produce.
What is needed, therefore, is an adjustable golf club that allows the weight of the golf club head to be independently moved in the heel/toe and front/rear directions. The club should be adjustable in this way so that the spin and fade/draw characteristics can be adjusted independently. Additionally, weights should be able to be engaged with the club head easily and securely. It is to such a golf club that embodiments of the present invention are primarily directed.